Pre-hardened steel composition and machine parts made therewith

ABSTRACT

A mud pump with components manufactured from high strength and toughness steel is disclosed. The mud pump includes a power end and a fluid end. The power end includes a motor, crankshaft rotationally engaged with the motor and a connecting rod rotationally engaged with the crank shaft. The fluid end includes a piston, a cylinder, a drilling fluid module, a discharge manifold, and a strainer cross. At least one of the plunger, the drilling fluid module, the discharge manifold, and the strainer cross has the following composition in weight percent: 0.25-0.55% carbon, 0.70-1.50% manganese, a maximum of 0.025% phosphorous, a maximum of 0.050% sulfur, a maximum of 0.80% silicon, 0.10-0.80% nickel, 1.40-2.20% chromium, 0.10-0.55% molybdenum, a maximum of 0.030% vanadium, a maximum of 0.35% copper, a maximum of 0.040% aluminum, a balance of iron, and incidental impurities.

FIELD OF THE DISCLOSURE

This disclosure generally relates to steel compositions and, more particularly, to machine parts made from said steel.

BACKGROUND OF THE DISCLOSURE

In the modern world, there is ever increasing demand for products derived from oil retrieved from deep within the earth. An oil well is a boring into the ground that is designed to bring petroleum oil hydrocarbons to the surface. The well is created by drilling a hole with a drilling rig that rotates a drill string with a bit attached. Drilling fluid also known as drilling mud is an essential element to creating the wellbore. The drilling fluid is pumped into the wellbore down the drill pipe and exits the drill bit at high pressure. The drilling fluid then circulates back to the surface through a space between the drill pipe and the outer surface of the well called the annulus, conveying cut rock with it. This process requires a reciprocating pump known as a mud pump.

The mud pump or drilling pump circulates the drilling mud downhole during drilling operations. The drilling mud is pumped downhole at pressures up to 7500 psi through the drill string and returns back to the surface via the well's annulus. This drilling mud circulation process performs numerous critical functions which include cooling the drill bit, cleaning the well bore of drill cuttings and providing hydrostatic pressure to prevent formation fluids from entering into the well bore.

Mud pumps are typically positive displacement, reciprocating pumps that are comprised of a power-end and fluid-end assembly. The power end includes a motor and a crankshaft rotationally engaged with the motor. Moreover, the power end may include a connection rod rotationally engaged with the crankshaft. The power-end converts the rotation of the crank shaft to a reciprocating motion by using a crosshead guide while the fluid-end utilizes this reciprocating action to achieve the function of pumping the pressurized mud. The fluid-end assembly is comprised of drilling fluid modules, cylinders, pistons, and valves. Many of the fluid-end assembly components are high-wear items. A key and necessary feature of a drilling pump is its ability to provide a constant flow rate of fluid at a specific pressure. Over the past century, numerous mud pump design configurations have been introduced but the most common designs on the market today are duplex, triplex, and quintuplex models.

Because the mud pump serves so many critical functions, drilling cannot take place without an operational mud pump. Production downtime can equate to hundreds of thousands of lost dollars per day. Ensuring minimal downtime of production machinery and other critical equipment is essential. Manufacturing critical parts out of alloys with high strength and toughness can increase the service life of these components and minimize downtime of crucial equipment. Furthermore, many of these components may also require hardened surfaces and high base strength and toughness to resist wear, fatigue and fracture. However, hardening these surfaces after fabricating the parts adds considerable expense. There is a need for a steel which allows for pre-hardening of block steel and maintains its hardness, strength and toughness during fabrication.

SUMMARY OF THE DISCLOSURE

In accordance with one aspect of the present disclosure, a mud pump is disclosed. The mud pump includes a power end and a fluid end. The power end includes a motor, a crankshaft rotationally engaged with the motor and a connecting rod rotationally engaged with the crank shaft. The fluid end is operatively connected to the power end and includes a piston, a cylinder configured to operatively engage the plunger, a drilling fluid module, a discharge manifold, and a strainer cross. At least one of the plunger, the drilling fluid module, the discharge manifold, and the strainer cross may be fabricated from a high strength and toughness steel composition having the following composition in percent by weight: 0.20-0.55% carbon, 0.70-1.50% manganese, a maximum of 0.025% phosphorous, a maximum of 0.050% sulfur, a maximum of 0.80% silicon, 0.10-0.80% nickel, 1.40-2.20% chromium, 0.10-0.55% molybdenum, a maximum of 0.030% vanadium, a maximum of 0.35% copper, a maximum of 0.040% aluminum, a balance of iron, and incidental impurities.

In accordance with another aspect of the present disclosure, a machine part is disclosed. The machine part is manufactured from a steel composition having the following composition in percent by weight: 0.20-0.55% carbon, 0.70-1.50% manganese, a maximum of 0.025% phosphorous, a maximum of 0.050% sulfur, a maximum of 0.80% silicon, 0.10-0.80% nickel, 1.40-2.20% chromium, 0.10-0.55% molybdenum, a maximum of 0.030% vanadium, a maximum of 0.35% copper, a maximum of 0.040% aluminum, a balance of iron, and incidental impurities.

In yet another aspect of the present disclosure, a steel composition is disclosed. The steel composition may have the following composition in percent by weight: 0.20-0.55% carbon, 0.70-1.50% manganese, a maximum of 0.025% phosphorous, a maximum of 0.050% sulfur, a maximum of 0.80% silicon, 0.10-0.80% nickel, 1.40-2.20% chromium, 0.10-0.55% molybdenum, a maximum of 0.030% vanadium, a maximum of 0.35% copper, a maximum of 0.040% aluminum, a balance of iron, and incidental impurities.

These and other aspects and features of the present disclosure will be more readily understood when read in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-sectional view of an exemplary mud pump, constructed in accordance with the present disclosure.

FIG. 2 is a flowchart of a series of steps that may be involved in manufacturing machine parts from high strength and toughness steel in accordance with the present disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

Referring now to FIG. 1, a side cross-sectional view of the exemplary mud pump 100 manufactured in accordance with the present disclosure is depicted. As represented therein, the mud pump 100 may include a power end 110 and a fluid end 120. The power end 110 is configured to provide work to the fluid end 120 thereby allowing the fluid end 120 to pump pressurized drilling mud into a wellbore. The power end 110 includes a motor (not shown) and a power end housing 130 which surrounds a main gear 140, crankshaft 150, and connecting rod 160. The crankshaft 150 is rotationally engaged with the motor via the main gear 140, and the connecting rod 160 is further rotationally engaged with the crankshaft 150. The connecting rod connects to an extension rod 170 in a crosshead guide 180. As the motor causes the main gear 140 to rotate, the crankshaft 150 rotates and causes the connecting rod 160 to move within the crosshead guide 180. This moves the extension rod 170 back and forth along a longitudinal axis of the pump 100. The extension rod 170 operatively connects the power end to the fluid end.

The fluid end 120 includes a fluid housing 190 at least partially surrounding the extension rod 170, a piston 200, a cylinder 210 and a drilling fluid module 220. The extension rod 170 is connected to the piston 200 and causes the piston 200 to move within the cylinder 210. While the current disclosure and drawings discuss a cylinder 210 and piston 200 arrangement, the current disclosure may also encompass an alternate cylinder and plunger arrangement. Accordingly, it is to be understood that the piston may be replaced by a plunger without departure from the scope of the current disclosure.

The drilling fluid module 220 is proximate the cylinder 210 and defines a flow passage 230 which may be pressurized and depressurized by the reciprocation of the piston 200 within the cylinder 210. The drilling fluid module may include a suction module 240 and a discharge module 250. As the piston 200 moves away from the drilling fluid module 220, drilling mud is drawn into the flow passage 230 through an inlet valve 260. As the piston moves towards the drilling fluid module 220, the drilling mud contained within the flow passage 230 is moved under pressure through an outlet valve 270 to a discharge manifold 280 and then to a wellbore (not shown). A strainer cross 290 may be located in the discharge manifold 280. Once in the wellbore, the drilling mud serves to cool and lubricate the drill bit, clean the well bore of drill cuttings and provide hydrostatic pressure to prevent formation fluids from entering into the wellbore.

Although the illustrated cross section shows only a single crankshaft, piston, and drilling fluid module, most mud pumps include 2-6 multiples of the described system driven by a single motor. These pumps (duplex, triplex, quintuplex etc.) provide a more consistent pressure to the wellbore. However, they also require correspondingly more components which suffer wear and must be replaced.

Because mud pumps must run continuously for extended periods, its components are subject to high stress. In order to avoid expensive downtime, these components must be made from high strength and toughness steel compositions such as that described below. The same high strength and toughness may also be of benefit for use in components for other oil exploration machinery and general industrial machinery components.

Many of these components also require hardened surfaces to resist wear. However, hardening these surfaces after manufacturing the parts adds considerable expense. The steel composition disclosed below allows for pre-hardening of block steel and maintains its hardness during fabrication.

The following composition of steel may be used for any components which require pre-hardened steel of a high strength and toughness, including but not limited to discharge manifolds, discharge and suction modules, strainer crosses, adapter spools, and similar machine parts. All percentages below are percent by weight.

Carbon 0.20-0.55% Manganese 0.70-1.50% Phosphorous 0.025% max. Sulfur 0.050% max. Silicon  0.80% max. Nickel 0.10-0.80% Chromium 1.40-2.20% Molybdenum 0.10-0.55% Vanadium 0.030% max. Copper  0.35% max. Aluminum 0.040% max. Iron balance, and Incidental impurities.

In a more preferred embodiment, the following composition with narrowed ranges within the above described composition may be used. All percentages describe percent by weight.

Carbon 0.25-0.35%  Manganese 1.2-1.45% Phosphorous 0.025% max. Sulfur 0.025% max. Silicon 0.15-0.4% Nickel 0.35-0.7% Chromium 1.7-2.05% Molybdenum 0.35-0.55%  Vanadium 0.030% max. Copper  0.35% max. Aluminum 0.040% max. Iron balance, and Incidental impurities.

In a yet more preferred embodiment, the following composition with narrowed ranges within the above described compositions may be used. All percentages describe percent by weight.

Carbon 0.30-0.35% Manganese  1.2-1.35% Phosphorous 0.010% max. Sulfur  0.01% max. Silicon 0.20-0.35% Nickel 0.55-0.65% Chromium 1.75-2.00% Molybdenum 0.40-0.50% Vanadium 0.010% max. Copper  0.20% max. Aluminum 0.025% max. Iron balance, and Incidental impurities.

In one specific embodiment, the following composition with a specific composition within the above described compositions may be used. All percentages describe percent by weight.

Carbon 0.33% Manganese 1.29% Phosphorous 0.008% Sulfur 0.003% Silicon 0.23% Nickel 0.64% Chromium 1.89% Molybdenum 0.43% Vanadium 0.004% Copper 0.15% Aluminum 0.021% Iron balance, and Incidental impurities.

Carbon is necessary to provide the required hardness and wear resistance. If carbon is significantly higher than 0.55% by weight, the component will exhibit reduced toughness and weldability. If substantially less than 0.20% by weight carbon is used, wear resistance and strength will not be suitable for service conditions to which the pump components are subjected. Preferably, a range of 0.25% to 0.35% by weight carbon is used to ensure acceptable wear resistance, hardness, and mechanical properties. Most preferably, carbon in the range of 0.30% to 0.35% should be used.

Manganese is essential for hardenability and as a deoxidizer in the steelmaking process. It also acts to control sulphides in forging operations. In combination with the other alloying elements, if significantly higher than 1.50% by weight is present, there is a risk that retained austenite will be present. If substantially less than 0.70% by weight manganese is present, the hardenability of the fabricated component will be lessened. Manganese also contributes to wear resistance, although to a lesser extent than other carbide formers. Preferably manganese will be present in the range of 1.20% to 1.45% by weight, and most preferably from 1.2% to 1.35% by weight.

Phosphorus can increase machinability but the detrimental effects of this element in engineering steels, such as an increase in ductile-brittle transition temperature and decreased ductility, outweigh any beneficial effects. Accordingly, the phosphorus content should not be more than the specified maximum of 0.025% by weight, and most preferably lower than 0.010% by weight.

In controlled quantities, sulfur can provide benefits to machinability, but it can also reduce mechanical properties. To maintain control of sulfides during processing it may be necessary to avoid a sulfur content over 0.05% by weight sulfur, preferably lower than 0.025% by weight, and most preferably lower than 0.010% by weight.

Silicon is specified for its deoxidizing ability in the steelmaking process. However, if present in substantially greater quantities than 0.80% by weight, there will be a predisposition towards embrittlement of the final product. Most preferably, silicon in the range of 0.15% to 0.40% by weight with an aim of 0.20% to 0.35% should be used.

Nickel aids in fracture toughness and impact strength of components, particularly at lower temperature. Furthermore, the addition of nickel increases the hardenability and allows for uniform properties throughout a cross section, facilitating a wider variety of manufacturing methods. Preferably, a range of 0.10% to 0.80% by weight nickel is used to ensure optimal properties. More preferably, nickel in the range of 0.35% to 0.70% should be used. Most preferably, nickel in the range of 0.55% to 0.65% may be used.

Chromium is necessary for hardenability, for carbide formation, and for wear resistance. If substantially more than the maximum of 2.20% by weight chromium is present, the hardening temperature would be too high for normal production heat treatment process. Below the specified minimum of 1.40% by weight chromium, the hardenability and wear resistance will be negatively affected. Preferably, chromium is present in the amount of 1.70% to 2.05% by weight, and most preferably from 1.75% to 2.00% by weight.

Molybdenum is a key element contributing to hardenability and wear resistance by the fact that it is a strong carbide former. Its beneficial effects are effective in the range of 0.10% to 0.55% by weight, but preferably it is maintained in the upper band of the range from 0.35% to 0.55% by weight, and most preferably in the range of 0.40% to 0.50% by weight.

Excessive quantities of vanadium are detrimental to ductility through the formation of an increased quantity of coarse carbides, and hence it is best to keep the vanadium at a maximum of 0.030% by weight. Accordingly, the vanadium content should not be more than the specified maximum of 0.030% by weight, and most preferably lower than 0.010% by weight.

Copper can create a predisposition towards embrittlement of the final product. Preferably, copper is present at an amount of no more than 0.35% by weight, and preferably lower than 0.20% by weight.

Aluminum is desirable for grain refinement but can have a detrimental effect on steel quality by causing the presence of aluminates, an undesirable impurity. It is therefore important to minimize the addition of aluminum to a maximum of 0.040% by weight in the final melt composition. Most preferably an aim of 0.020% by weight aluminum will achieve grain refinement.

In all the described compositions, the balance of the steel is made up of iron. Some incidental impurities may also be present.

In order to exhibit the required operating characteristics described above, a mud pump component or other machine part should be produced from a block of steel manufactured by the method depicted in FIG. 2. The method includes:

-   -   a. melting the bulk of the steel composition containing a         majority of the alloy ingredients in an electric arc furnace to         produce a steel melt suitable for tapping into a receptacle         (block 502),     -   b. thereafter heating, alloying, and refining the heat to bring         the heat to its final composition (block 504),     -   c. vacuum degassing, teeming, and casting the heat by bottom         pouring practices to form ingots (block 506),     -   d. hot working the ingots to form a mud pump component, machine         part, or block (block 508), and     -   e. thereafter heat treating the mud pump component, machine         part, or block by fully austenitizing, rapidly quenching in a         liquid, preferably water, and subsequently tempering to form a         final hot work product (block 510)

In some embodiments, during the step of heat treating the block, the final hot worked product should be subjected to austenitizing at a temperature of between 800° and 950° C. (block 512), quenching in water (block 514), and tempering at a temperature of between 450° and 700° C. (block 516). Following said treatment, the resultant product will exhibit a microstructure comprising mostly tempered martensite and bainite and possibly a mixture of tempered martensite, bainite and pearlite which will be deeper than ¼ of the thickness of the block.

The block may subsequently be further worked to form mud pump components and other machine parts without losing the desired properties. 

1.-15. (canceled)
 16. A steel comprising the following composition in percent by weight: C 0.20-0.55%, Mn 0.70-1.50%, P 0.025% max., S 0.050% max., Si  0.80% max., Ni 0.10-0.80%, Cr 1.40-2.20%, Mo 0.10-0.55%, V 0.030% max., Cu  0.35% max., Al 0.040% max., Fe balance, and incidental impurities.


17. The steel of claim 16, wherein the steel composition comprises the following composition in percent by weight: C 0.20-0.35%, Mn 1.20-1.45%, P 0.025% max., S 0.025% max., Si 0.15-0.40%, Ni 0.35-0.70%, Cr 1.70-2.05%, Mo 0.35-0.55%, V 0.030% max., Cu  0.35% max., Al 0.040% max., Fe balance, and incidental impurities.


18. The steel of claim 16, wherein the steel composition comprises the following composition in percent by weight: C 0.30-0.35%, Mn 1.20-1.35%, P 0.010% max., S 0.010% max., Si 0.20-0.35%, Ni 0.55-0.65%, Cr 1.75-2.00%, Mo 0.40-0.50%, V 0.010% max., Cu  0.20% max., Al 0.025% max., Fe balance, and incidental impurities.


19. The steel of claim 16, wherein a block of the steel composition is prepared in an electric arc furnace by: a. melting the bulk of the steel composition containing the majority of the alloy ingredients to produce a steel melt suitable for tapping into a receptacle, b. thereafter tapping, heating, alloying, and refining the heat to bring the heat to its final composition, c. vacuum degassing, teeming and casting the heat by bottom pouring practices to form an ingot, d. hot working the ingot to form a block, and e. thereafter heat treating the block by water quenching and tempering to form a final hot work product.
 20. The steel of claim 19, wherein the final hot work product is subsequently subjected to: austenitizing at a temperature of between 800° and 950° C., quenching in water, and tempering at a temperature of between 500° and 700° C. to form a microstructure consisting mostly of martensite and bainite or a mixture of martensite, bainite and perlite which will be deeper than ¼ of the thickness of the block.
 21. The steel of claim 17, wherein a block of the steel composition is prepared in an electric arc furnace by: a. melting the bulk of the steel composition containing the majority of the alloy ingredients to produce a steel melt suitable for tapping into a receptacle, b. thereafter tapping, heating, alloying, and refining the heat to bring the heat to its final composition, c. vacuum degassing, teeming and casting the heat by bottom pouring practices to form an ingot, d. hot working the ingot to form a block, and e. thereafter heat treating the block by water quenching and tempering to form a final hot work product.
 22. The steel of claim 21, wherein the final hot work product is subsequently subjected to: austenitizing at a temperature of between 800° and 950° C., quenching in water, and tempering at a temperature of between 500° and 700° C. to form a microstructure consisting mostly of martensite and bainite or a mixture of martensite, bainite and perlite which will be deeper than ¼ of the thickness of the block.
 23. The steel of claim 18, wherein a block of the steel composition is prepared in an electric arc furnace by: a. melting the bulk of the steel composition containing the majority of the alloy ingredients to produce a steel melt suitable for tapping into a receptacle, b. thereafter tapping, heating, alloying, and refining the heat to bring the heat to its final composition, c. vacuum degassing, teeming and casting the heat by bottom pouring practices to form an ingot, d. hot working the ingot to form a block, and e. thereafter heat treating the block by water quenching and tempering to form a final hot work product.
 24. The steel of claim 23, wherein the final hot work product is subsequently subjected to: austenitizing at a temperature of between 800° and 950° C., quenching in water, and tempering at a temperature of between 500° and 700° C. to form a microstructure consisting mostly of martensite and bainite or a mixture of martensite, bainite and perlite which will be deeper than ¼ of the thickness of the block.
 25. The block of steel of claim 20, the steel is further worked to form a component of a mud pump.
 26. The block of steel of claim 20, the steel is further worked to form a component of a machine part.
 27. The block of steel of claim 20, the steel is further worked into a discharge manifold.
 28. The block of steel of claim 20, the steel is further worked into a a strainer cross.
 29. The block of steel of claim 20, the steel is further worked into a component of an oil field exploration machinery.
 30. The block of steel of claim 20, the steel is further worked into an adapter spool.
 31. The block of steel of claim 20, the steel is further worked into a piston or a cylinder
 32. The block of steel of claim 20, the steel is further worked into a crankshaft.
 33. The block of steel of claim 20, the steel is further worked into a drilling fluid module.
 34. The block of steel of claim 20, the steel is further worked into a plunger.
 35. The block of steel of claim 22, the steel is further worked to form a component of a mud pump. 